Hurricanes Could Bust Gulf Oil Pipelines

by Andrea Thompson | June 14, 2010 06:47am ET

Hurricanes roaring across the Gulf of Mexico create strong enough
underwater waves to dig up and potentially bust open oil pipelines that
run across the ocean floor, according to a new study that recorded the
currents created by the massive storms.

The massive Deepwater Horizon oil spill in the Gulf has focused attentions on the potential for more such environmental disasters, particularly now that the 2010 hurricane season
has started. Scientists and officials are not only worried about how a
storm might exacerbate the current spill, but the potential for it to
cause another one, possibly by causing a rupture in an oil pipeline.

At least 31,000 miles (50,000 kilometers) of pipelines snake across
the floor of the Gulf, according to the Minerals Management Service,
and hurricanes have long been known to cause a range of damage to them,
from dents to full ruptures.

After 2004's Hurricane Ivan, the MMS cited 168 pipeline damage
reports; after Rita in 2005, it was 243; and there were 299 in the wake
of devastating Hurricane Katrina, said Bill Teague of the U.S. Naval
Research Laboratory at Stennis Space Center in Mississippi.

The numbers Teague cited were based on a 2006 MMS report stated that
Ivan "produced high levels of pipeline damage, many resulting from
mudslides and excessive movement in the Mississippi Delta region." The
report listed separations of pipelines and rises as the No. 1 type of
damage reported from the 168 cases, with "unknown" coming in at No. 2
with 25 incidents and bent risers at No. 3 with 24 reports. Other types
of damage included dents, pipeline movements and kinks.

Teague's study did not investigate whether any of these cases of damage had resulted in a leak.

Ivan's scouring

Teague and his colleagues got an unprecedented view of the forces
that can cause this damage when the eye of Ivan, a Category 4 storm,
passed over a network of sensors moored to the ocean floor that were
put in place to monitor currents along the continental shelf of the
Gulf.

The sensors showed that strong currents along the seafloor scoured the seabed, picking up sediment from some places and piling it up in others.

The howling winds of hurricanes can generate strong currents, but
the researchers found that it was the surface waves that Ivan generated
that in turn created the most powerful currents on the seafloor. These
waves can rise to 66 feet (20 meters) or more above the ocean's surface
— the team measured one at 91 feet (28 meters), which Teague said he
thinks is the highest wave ever measured by instruments.

"That is a big wave," he said.

The currents generated by the waves loft large amounts of sediments,
which clouded the water up to 82 feet (25 meters) above the seafloor.
Sediments were washed away from underneath the team's sensors, causing
them to sink down to the new ocean bottom.

The scouring of sediments could create underwater mudslides — akin
to avalanches on land — that could cause damage to oil pipelines.

Persistent effect

Because the waves have a much more powerful effect on this seafloor
scouring, even a weaker, slow-moving hurricane could cause damage,
because its speed would allow it time to build up large waves, even if
its winds weren't as fierce.

Another point that was learned from the study of Ivan's scouring was
that the effects persisted for more than a week after the storm had
passed.

The study couldn't say the exact ways in which pipes are damaged or
what the likelihood of having a major rupture and subsequent spill
would be, said Teague, who could smell the current oil spill from his
office just 10 to 15 miles from the Gulf coast. But the researchers
hope that their study could help engineering efforts to protect
structures and pipelines in the face of an impending storm.

The study is detailed in the June 10 issue of the journal Geophysical Research Letters.

Andrea Thompson

Andrea graduated from Georgia Tech with a B.S. in Earth and Atmospheric Sciences in 2004 and a Master's in the same subject in 2006. She attended the Science, Health and Environmental Reporting Program at New York University and graduated with a Master of Arts in 2006.